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.\" ========================================================================
.\"
.IX Title "virt-diff 1"
.TH virt-diff 1 2024-01-16 guestfs-tools-1.52.0 "Virtualization Support"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
virt\-diff \- Differences between files in two virtual machines
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& virt\-diff [\-\-options] \-d domain1 \-D domain2
\&
\& virt\-diff [\-\-options] \-a disk1.img [\-a ...] \-A disk2.img [\-A ...]
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
\&\f(CW\*(C`virt\-diff\*(C'\fR lists the differences between files in two virtual
machines or disk images.  The usual use case is to show the
changes in a VM after it has been running for a while, by taking
a snapshot, running the VM, and then using this tool to show
what changed between the new VM state and the old snapshot.
.PP
This tool will find differences in filenames, file sizes, checksums,
extended attributes, file content and more from a virtual machine or
disk image.  However it \fBdoes not\fR look at the boot loader, unused
space between partitions or within filesystems, "hidden" sectors and
so on.  In other words, it is not a security or forensics tool.
.PP
To specify two guests, you have to use the \fI\-a\fR or \fI\-d\fR option(s)
for the first guest, and the \fI\-A\fR or \fI\-D\fR option(s) for the second
guest.  The common case is:
.PP
.Vb 1
\& virt\-diff \-a old.img \-A new.img
.Ve
.PP
or using names known to libvirt:
.PP
.Vb 1
\& virt\-diff \-d oldguest \-D newguest
.Ve
.SH OPTIONS
.IX Header "OPTIONS"
.IP \fB\-\-help\fR 4
.IX Item "--help"
Display brief help.
.IP "\fB\-a\fR file" 4
.IX Item "-a file"
.PD 0
.IP "\fB\-\-add\fR file" 4
.IX Item "--add file"
.PD
Add \fIfile\fR which should be a disk image from the first virtual
machine.  If the virtual machine has multiple block devices, you must
supply all of them with separate \fI\-a\fR options.
.Sp
The format of the disk image is auto-detected.  To override this and
force a particular format use the \fI\-\-format=..\fR option.
.IP "\fB\-a\fR URI" 4
.IX Item "-a URI"
.PD 0
.IP "\fB\-\-add\fR URI" 4
.IX Item "--add URI"
.PD
Add a remote disk.  See "ADDING REMOTE STORAGE" in \fBguestfish\fR\|(1).
.IP \fB\-\-all\fR 4
.IX Item "--all"
Same as \fI\-\-extra\-stats\fR \fI\-\-times\fR \fI\-\-uids\fR \fI\-\-xattrs\fR.
.IP \fB\-\-atime\fR 4
.IX Item "--atime"
The default is to ignore changes in file access times, since those are
unlikely to be interesting.  Using this flag shows atime differences
as well.
.IP "\fB\-A\fR file" 4
.IX Item "-A file"
.PD 0
.IP "\fB\-A\fR URI" 4
.IX Item "-A URI"
.PD
Add a disk image from the second virtual machine.
.IP \fB\-\-blocksize=512\fR 4
.IX Item "--blocksize=512"
.PD 0
.IP \fB\-\-blocksize=4096\fR 4
.IX Item "--blocksize=4096"
.IP \fB\-\-blocksize\fR 4
.IX Item "--blocksize"
.PD
This parameter sets the sector size of the disk image.  It affects all
explicitly added subsequent disks after this parameter.  Using
\&\fI\-\-blocksize\fR with no argument switches the disk sector size to the
default value which is usually 512 bytes.  See also
"guestfs_add_drive_opts" in \fBguestfs\fR\|(3).
.IP \fB\-\-checksum\fR 4
.IX Item "--checksum"
.PD 0
.IP \fB\-\-checksum=crc|md5|sha1|sha224|sha256|sha384|sha512\fR 4
.IX Item "--checksum=crc|md5|sha1|sha224|sha256|sha384|sha512"
.PD
Use a checksum over file contents to detect when regular files have
changed content.
.Sp
With no argument, this defaults to using \fImd5\fR.  Using an argument,
you can select the checksum type to use.  If the flag is omitted then
file times and size are used to determine if a file has changed.
.IP "\fB\-c\fR URI" 4
.IX Item "-c URI"
.PD 0
.IP "\fB\-\-connect\fR URI" 4
.IX Item "--connect URI"
.PD
If using libvirt, connect to the given \fIURI\fR.  If omitted, then we
connect to the default libvirt hypervisor.
.Sp
If you specify guest block devices directly (\fI\-a\fR), then libvirt is
not used at all.
.IP \fB\-\-csv\fR 4
.IX Item "--csv"
Write out the results in CSV format (comma-separated values).  This
format can be imported easily into databases and spreadsheets, but
read "NOTE ABOUT CSV FORMAT" below.
.IP \fB\-\-dir\-links\fR 4
.IX Item "--dir-links"
The default is to ignore changes in the number of links in directory
entries, since those are unlikely to be interesting.  Using this flag
shows changes to the nlink field of directories.
.IP \fB\-\-dir\-times\fR 4
.IX Item "--dir-times"
The default is to ignore changed times on directory entries, since
those are unlikely to be interesting.  Using this flag shows changes
to the time fields of directories.
.IP "\fB\-d\fR guest" 4
.IX Item "-d guest"
.PD 0
.IP "\fB\-\-domain\fR guest" 4
.IX Item "--domain guest"
.PD
Add all the disks from the named libvirt guest, as the first guest.
Domain UUIDs can be used instead of names.
.IP "\fB\-D\fR guest" 4
.IX Item "-D guest"
Add all the disks from the named libvirt guest, as the second guest.
Domain UUIDs can be used instead of names.
.IP \fB\-\-echo\-keys\fR 4
.IX Item "--echo-keys"
When prompting for keys and passphrases, virt-diff normally turns
echoing off so you cannot see what you are typing.  If you are not
worried about Tempest attacks and there is no one else in the room you
can specify this flag to see what you are typing.
.IP \fB\-\-extra\-stats\fR 4
.IX Item "--extra-stats"
Display extra stats.
.IP \fB\-\-format=raw|qcow2|..\fR 4
.IX Item "--format=raw|qcow2|.."
.PD 0
.IP \fB\-\-format\fR 4
.IX Item "--format"
.PD
The default for the \fI\-a\fR/\fI\-A\fR option is to auto-detect the format of
the disk image.  Using this forces the disk format for \fI\-a\fR/\fI\-A\fR
options which follow on the command line.  Using \fI\-\-format\fR with no
argument switches back to auto-detection for subsequent \fI\-a\fR/\fI\-A\fR
options.
.Sp
For example:
.Sp
.Vb 1
\& virt\-diff \-\-format=raw \-a disk.img [...]
.Ve
.Sp
forces raw format (no auto-detection) for \fIdisk.img\fR.
.Sp
.Vb 1
\& virt\-diff \-\-format=raw \-a disk.img \-\-format \-a another.img [...]
.Ve
.Sp
forces raw format (no auto-detection) for \fIdisk.img\fR and reverts to
auto-detection for \fIanother.img\fR.
.Sp
If you have untrusted raw-format guest disk images, you should use
this option to specify the disk format.  This avoids a possible
security problem with malicious guests (CVE\-2010\-3851).
.IP \fB\-h\fR 4
.IX Item "-h"
.PD 0
.IP \fB\-\-human\-readable\fR 4
.IX Item "--human-readable"
.PD
Display file sizes in human-readable format.
.IP "\fB\-\-key\fR SELECTOR" 4
.IX Item "--key SELECTOR"
Specify a key for LUKS, to automatically open a LUKS device when using
the inspection.
.RS 4
.IP "\fB\-\-key\fR NAME\fB:key:\fRKEY_STRING" 4
.IX Item "--key NAME:key:KEY_STRING"
.PD 0
.IP "\fB\-\-key\fR UUID\fB:key:\fRKEY_STRING" 4
.IX Item "--key UUID:key:KEY_STRING"
.IP "\fB\-\-key\fR \fBall:key:\fRKEY_STRING" 4
.IX Item "--key all:key:KEY_STRING"
.PD
\&\f(CW\*(C`NAME\*(C'\fR is the libguestfs device name (eg. \f(CW\*(C`/dev/sda1\*(C'\fR).  \f(CW\*(C`UUID\*(C'\fR is
the device UUID.  \f(CW\*(C`all\*(C'\fR means try the key against any encrypted
device.
.Sp
Use the specified \f(CW\*(C`KEY_STRING\*(C'\fR as passphrase.
.IP "\fB\-\-key\fR NAME\fB:file:\fRFILENAME" 4
.IX Item "--key NAME:file:FILENAME"
.PD 0
.IP "\fB\-\-key\fR UUID\fB:file:\fRFILENAME" 4
.IX Item "--key UUID:file:FILENAME"
.IP "\fB\-\-key\fR \fBall:file:\fRFILENAME" 4
.IX Item "--key all:file:FILENAME"
.PD
Read the passphrase from \fIFILENAME\fR.
.IP "\fB\-\-key\fR NAME\fB:clevis\fR" 4
.IX Item "--key NAME:clevis"
.PD 0
.IP "\fB\-\-key\fR UUID\fB:clevis\fR" 4
.IX Item "--key UUID:clevis"
.IP "\fB\-\-key\fR \fBall:clevis\fR" 4
.IX Item "--key all:clevis"
.PD
Attempt passphrase-less unlocking for the device with Clevis, over the
network.  Please refer to "ENCRYPTED DISKS" in \fBguestfs\fR\|(3) for more
information on network-bound disk encryption (NBDE).
.Sp
Note that if any such option is present on the command line, QEMU user
networking will be automatically enabled for the libguestfs appliance.
.RE
.RS 4
.RE
.IP \fB\-\-keys\-from\-stdin\fR 4
.IX Item "--keys-from-stdin"
Read key or passphrase parameters from stdin.  The default is
to try to read passphrases from the user by opening \fI/dev/tty\fR.
.Sp
If there are multiple encrypted devices then you may need to supply
multiple keys on stdin, one per line.
.IP \fB\-\-times\fR 4
.IX Item "--times"
Display time fields.
.IP \fB\-\-time\-days\fR 4
.IX Item "--time-days"
Display time fields as days before now (negative if in the future).
.Sp
Note that \f(CW0\fR in output means "up to 1 day before now", or that the
age of the file is between 0 and 86399 seconds.
.IP \fB\-\-time\-relative\fR 4
.IX Item "--time-relative"
Display time fields as seconds before now (negative if in the future).
.IP \fB\-\-time\-t\fR 4
.IX Item "--time-t"
Display time fields as seconds since the Unix epoch.
.IP \fB\-\-uids\fR 4
.IX Item "--uids"
Display UID and GID fields.
.IP \fB\-v\fR 4
.IX Item "-v"
.PD 0
.IP \fB\-\-verbose\fR 4
.IX Item "--verbose"
.PD
Enable verbose messages for debugging.
.IP \fB\-V\fR 4
.IX Item "-V"
.PD 0
.IP \fB\-\-version\fR 4
.IX Item "--version"
.PD
Display version number and exit.
.IP \fB\-x\fR 4
.IX Item "-x"
Enable tracing of libguestfs API calls.
.IP \fB\-\-xattrs\fR 4
.IX Item "--xattrs"
Display extended attributes.
.SH "NOTE ABOUT CSV FORMAT"
.IX Header "NOTE ABOUT CSV FORMAT"
Comma-separated values (CSV) is a deceptive format.  It \fIseems\fR like
it should be easy to parse, but it is definitely not easy to parse.
.PP
Myth: Just split fields at commas.  Reality: This does \fInot\fR work
reliably.  This example has two columns:
.PP
.Vb 1
\& "foo,bar",baz
.Ve
.PP
Myth: Read the file one line at a time.  Reality: This does \fInot\fR
work reliably.  This example has one row:
.PP
.Vb 2
\& "foo
\& bar",baz
.Ve
.PP
For shell scripts, use \f(CW\*(C`csvtool\*(C'\fR (https://github.com/Chris00/ocaml\-csv
also packaged in major Linux distributions).
.PP
For other languages, use a CSV processing library (eg. \f(CW\*(C`Text::CSV\*(C'\fR
for Perl or Python’s built-in csv library).
.PP
Most spreadsheets and databases can import CSV directly.
.SH "EXIT STATUS"
.IX Header "EXIT STATUS"
This program returns 0 if successful, or non-zero if there was an
error.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBguestfs\fR\|(3),
\&\fBguestfish\fR\|(1),
\&\fBvirt\-cat\fR\|(1),
\&\fBvirt\-copy\-out\fR\|(1),
\&\fBvirt\-ls\fR\|(1),
\&\fBvirt\-tar\-out\fR\|(1),
http://libguestfs.org/.
.SH AUTHOR
.IX Header "AUTHOR"
Richard W.M. Jones http://people.redhat.com/~rjones/
.SH COPYRIGHT
.IX Header "COPYRIGHT"
Copyright (C) 2009\-2023 Red Hat Inc.
.SH LICENSE
.IX Header "LICENSE"
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
.PP
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.
.PP
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110\-1301 USA.
.SH BUGS
.IX Header "BUGS"
To get a list of bugs against libguestfs, use this link:
https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
.PP
To report a new bug against libguestfs, use this link:
https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
.PP
When reporting a bug, please supply:
.IP \(bu 4
The version of libguestfs.
.IP \(bu 4
Where you got libguestfs (eg. which Linux distro, compiled from source, etc)
.IP \(bu 4
Describe the bug accurately and give a way to reproduce it.
.IP \(bu 4
Run \fBlibguestfs\-test\-tool\fR\|(1) and paste the \fBcomplete, unedited\fR
output into the bug report.